Molten metal supplying apparatus

ABSTRACT

Described is an apparatus for supplying molten metal to devices, apparatus, machines, etc., which accept charges or shots of metal on an intermittent basis, such as die caster and certain forging machines, for example. An induction crucible encircling both a single-charge measuring chamber means and a discharge control valve means melts and/or final heats the metal in accord with demand rate and under precise temperature control, and delivers measured single-charge volumes of such molten metal to suit the demand charge volume conditions. Included is a means which automatically furnishes input metal to the crucible commensurate with its discharge rate.

United States Patent Harry A. Lord Wake Forest, N.C.

Aug. 14, 1969 Jan. 4, 1972 Westinghouse Electric Corporation Pittsburgh, Pa.

[72] Inventor [21 1 Appl. No. [22] Filed [45] Patented [73] Assignee [54] MOLTEN METAL SUPPLYING APPARATUS 1 Claim, 4 Drawing Figs.

[52] US. Cl 266/38, 164/337 [51] Int. Cl C21b 7/14 [50] Field of Search 266/38, 34 A, 34, DIG. 2, 33 R; 164/335, 337

[56] References Cited UNITED STATES PATENTS 2,290,083 7/ 1942 Webster 164/337 2,446,637 8/1948 Crampton et al. 266/33 R 2,636,219 8/1953 Beamer et a1 266/34 R 2,668,994 2/1954 Hansen 266/38 2,768,413 10/1956 Alexanderson. 164/337 7/1958 7 Gaffney 266/38 3,060,065 10/1962 Orem 266/33 R 3,235,243 2/1966 Tay1or..... 266/34 R 3,334,408 8/1967 Ayers 266/34D1G. 2 3,352,351 11/1967 SiCbCIL... 164/335 3,384,362 5/1968 Philbrick.... 266/34 R 3,470,941 10/1969 Thompson 164/337 FOREIGN PATENTS 833,956 5/ 1960 Great Britain 266/34 R Primary Examiner-Gerald A. Dost AttameysF. H. Henson and E. P. Klipfel ABSTRACT: Described is an apparatus for supplying molten metal to devices, apparatus, machines, etc., which accept charges or shots of metal on an intermittent basis, such as die caster and certain forging machines, for example. An induction crucible encircling both a single-charge measuring chamber means and a discharge control valve means melts and/or final heats the metal in accord with demand rate and under precise temperature control, and delivers measured single-charge volumes of such molten metal to suit the demand charge volume conditions. lncluded is a means which automatically furnishes input metal to the crucible commensurate with its discharge rate.

SHEET 1 OF 2 FIG. 1

' Mu FIG. 2 10 0 MM,

9: W W60 62 I Z 58 I. 56

, TEMPERATURE I SENSOR v HEAT'NG' V L INDUCTION POWER HEATING POWER REGULATOR COL souRcE ...ET A A CRUCIBLE INPUT METAL FEED MEANS FIG. 4

SET'EEEEEREB R g MEANS MOLTEN METAL SUPPLYING APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention Apparatus for supplying intermittently demanded molten metal at regular intervals and at regulated temperatures.

2. Description of the Prior Art In certain production casting and forging lines, for example, molten metal is required at intervals for charging the particular molten-metal-demanding device involved. Under normal circumstances, such apparatus will have an average demand rate for molten metal at somewhat precise temperature condition requisite to satisfactory perfonnance. It has been a common practice to melt scrap or other forms of the required metal initially in a breakdown furnace and to then admit molten metal therefrom into a holding furnace of larger capacity, often several times that of the breakdown furnace and hundreds of times the single shot capacity of the molten-metal-demanding apparatus supplied therefrom; the larger capacity holding furnace affording a temperature stabilizing influence on the molten metal by virtue of the massiveness of such metal and its isolation from introduction of the solid input metal at the breakdown furnace.

It also has been a practice to rely upon the timed opening of a communication from the holding furnace to the moltenmetal-demanding apparatus for charging the latter with molten metal at the required intervals. With such technique of charging control, a premium is placed on judgement of an operator to properly control the timing of the molten charge flow under variable conditions of flow passage cleanliness which affects the flow rate, and/or to properly maintain such passage consistently clear of any residue. Otherwise, the apparatus may become undercharged or overcharged, which in the former case can result in a faulty product and, in the latter case, can result in spillage of molten metal.

Still further, difficulty can be experienced in operation of valves for controlling on-off flow of molten metal as a result of solid metal deposits on valve regions that tend to cool in the shut-off state of such valves.

SUMMARY The present invention overcomes the undesirable aspects of the previous typical molten metal supply system discussed above by providing; an induction crucible capable of rapid response and precise temperature regulation for melting and/or momentarily holding a small volume of molten metal, preferably less than times the single-charge capacity of the molten-metal-demanding apparatus it supplies to intermittently, while maintaining temperature of such metal uniform by the heating and stirring effect produced by the crucibles induction heating coil; a measuring means including a fillable measuring chamber or volume to dole out a precise amount of molten metal suited to the metal charge volume capacity of the molten-metaI-demanding device supplied by the apparatus; and a valve means, heat-protected against freezeup, for periodically and consecutively admitting the molten crucible metal into and out of the measuring chamber for intermittently charging such molten-metal-demanding apparatus. Inclusion of automatically regulated means for feeding metal to the crucible further enhances utility of the apparatus.

BRIEF DESCRIPTION OF THE DRAWING FIGS. 1 and 2 are elevation views of two exemplifications of a molten metal supplying apparatus embodying the invention;

FIG. 3 is a vertical axial section view of a combined induction crucible, measuring chamber, and metal delivery control valve means embodied in the invention; and

FIG. 4 is a block diagram of a control means for the apparatus of FIGS. 1 and 2.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring'to FIG. 1, the apparatus of the present invention is for the purpose of supplying molten metal to molten-metalusing apparatus, machines, or devices 5 such as certain types of die casting machines, forging machines, etc., which, during production operation, are to be charged at regular intervals during their operating cycles with molten metal, such aluminum, brass, etc., in an amount which is required to fill the same with a single shot and which amount is not varied from cycle to cycle. Often a casting machine or device will be of the vacuum type.

It is an objective of the present invention to provide an apparatus for supplying molten metal to such intermittently demanding devices or machines 5 on a semicontinuous basis at carefully regulated molten metal temperatures without need for large standby volumes of molten metal. In accord with such objectives, the apparatus of the present invention includes an induction crucible 7 which is of relatively small volume in comparison to the hourly or daily molten metal demands of the molten-metal-using apparatus 5 with which it is affiliated. In accord with different embodiments of the present invention, input metal to the crucible 7 may be: molten metal 8, such as from a breakdown furnace 9 shown in FIG. 1; preheated solid metal such as in the form of particles or pellets 10 as shown leaving a continuous radiant furnace means 11 in FIG. 2; or solid unheated metal in suitable form, including pellets. Crucible 7 will melt and/or momentarily hold such input metal in a molten state while providing carefully regulated and distributed temperature conditions, in readiness for supply to the metal using device or machine 5. Preferably the induction crucible 7 will be used with only one or two such machines 5, although it will be appreciated that any such machine may include a plurality of cavities therein to be filled simultaneously at any given delivery occasion from the crucible. In any event, input metal will be supplied to crucible 7 during operation of the apparatus 5 at a rate equal to the demand rate of such apparatus.

In employment of the induction crucible 7 with an aluminum die casting machine, for example, as the molten-metalusing apparatus 5, and a breakdown furnace 9, FIG. 1, is employed to initially melt the aluminum, the molten metal 8, aluminum, is withdrawn by means of a molten metal pump means 14 and conveyed by a feed conduit 15 to the induction crucible 7 where a vernier adjustment of the temperature of such molten metal is obtained, together with induction stirring of such molten metal. Alternatively, FIG. 2, pellets 10 of aluminum may be preheated by way of radiant furnace means 11 to raise the temperature of such aluminum to such as 900 F. prior to introduction to the induction crucible 7 where the aluminum will be melted and held momentarily at such as l,200 F. 1 several degrees. For any given molten metal demand rate from the induction crucible 7 the energizing power made available for its operation will be in accord with its mode of input supply.

Referring particularly to FIG. 3, the induction crucible 7 as exemplified therein is in generally cylindrical form. To afford a capability of supplying molten aluminum at a rate of such as 400 lbs./hr., for example, it need be approximately only slightly greater than 1 foot long and a diameter of approximately 1 foot encircled by a helical induction coil 18 which extends substantially the full length of the crucible. The crucible 7 is composed of a material suitable to withstand the heat of the molten metal contained therein, for example in the case of aluminum such crucible may be made of a commercially available graphite clay material, which at the same time will not shield the magnetic flux produced by the induction coil 18 from the metal within such crucible. The coil 18, by way of example, may include some 30 turns of hollow copper tubing that enables it to be water cooled in accord with the usual practice. In the case of accepting molten metal input as exemplified in FIG. 1 the power requirements for the induction coil 18 will be relatively low as compared to accepting solid input metal for meltdown and regulation of melt temperature for any given demand rate.

Also included in the apparatus of the present invention is a measuring means 20 which preferably, in accord with the showing of FIG. 3, is disposed centrally within the crucible 7 to be encircled by molten metal 21. Means 20 includes a container member 23 defining the outer periphery of a measuring chamber of volume 24, and a coaxial arrangement of stopper valves 26 and 27 in the form of graphite rods which are movable in an axial direction to control the admittance of molten metal 21 from the encircling crucible 7 into the measuring chamber 24 to fill same and the subsequent release of such measured amount of molten metal from such chamber by way of delivery nozzle 30 to the metal-using devices, machine, or apparatus 5.

The chamber-defining container member 23 preferably is cup-shaped and includes an open-top cylindrical wall portion integrally joined to the delivery nozzle 30 at its bottom; which nozzle extends downwardly through a suitable opening in the bottom wall 32 of the outer crucible 7. The bottom wall of the inner member 23 has a conical stopper valve seat 34 encircling the top end of a delivery passage 36 which extends centrally through the delivery nozzle 30. The central stopper valve 26 in turn has a conical bottom end for cooperation with the conical seat 34 to control the exiting of the measured amount of molten metal with which chamber 24 is filled. The encircling coaxial stopper valve 27 fits with a slight radial clearance around the inner stopper valve 26 and cooperates with the upper annular rim 40 of the member 23 to control the filling of chamber 24 with the encircling molten metal 21 from the outer crucible 7 and isolation of such chamber from such encircling crucible metal during emptying of chamber 24. Integral extensions of the valves 26, and 27 act as actuating stems 42 and 44 that extend up and through cover members atop of the outer crucible 7 and are provided with suitable separately operable actuating means in such form as pneumatic cylinders 46 and 48, FIG. 1, coupled to such stopper valve stems via suitable linkages enabling axial movement thereof.

When the crucible 7 is employed to melt the input metal as in the arrangement in FIG. 2, for example, inclusion of a slag screen 50 may be advantageous. The slag screen exemplified is in the form of a perforated cylindrical member disposed in the crucible 7 in encirclement of the measuring member 23 to permit passage of molten metal 21 from its exterior to its interior and thereby to the measuring chamber 24 within the member 24 when valve 27 is unseated, preventing such passage of any slag; it being appreciated that input metal will be introduced to crucible 7 outside the periphery of slag screen 50.

In installations where the crucible 7 effectuates meltdown of the input metal thereto, such input metal, being in solid form, will most conveniently be handled if it is in particle form, as exemplified in FIG. 2. However, it may be desirable to include use of scrap metal which may exist from time to time in the locale of such installation, and such scrap metal most often will be of such a shape and size that cannot conveniently be accommodated by the relatively small crucible 7 and/or automatic feed means of the present invention. In such case, it can become worthwhile to convert such scrap metal initially into particle form such as by use of a method set forth in Beamer et al. US. Pat. No. 2,636,219, which involves melting of such scrap metal, pouring the molten metal through a water jet ring that breaks up the molten metal stream into soft spherical particles, and solidifying such particles in a water tank into which such particles are allowed to fall.

In operation, input metal is added to the crucible 7 automatically to maintain the level of molten metal therein substantially constant. Such as a float-actuated switch device 52 shown schematically in FIG. 3 and indicated in block diagram form in FIG. 4, can provide for controlling operation of the crucible input metal feed means. In the case of molten input metal, the level sensing means 52 will control operation of the molten metal pump 14 to cause transfer of molten metal from the interior of the breakdown furnace to the induction crucible 7, and in the case of solid input metal, such molten metal level sensing means 52 will control the operation of a motor 56, FIG. 2, driving such as a conveyor belt 58 that transfers particulate metal from an input hopper 60 to a discharge nozzle 62 or chute leading into the top of the crucible 7. Such metal may or may not be reheated by such as the radiant furnace means 11 shown in FIG. 2, according to the desired operating parameters of the system.

The helical induction heating coil 18 for the crucible 8 is energized with alternating current power of a suitable frequency such as 3,000 to 10,000 Hz. and at a power level suitable to obtain and/or maintain, as the case may be, the metal in crucible 7 in a molten agitated state. A temperature sensor, in the form of an infrared pyrometer 65. for example, FIG. 3, serves to sense temperature of the molten metal by observation of such metal through a window 66 in a cover wall on top of the crucible. As indicated schematically in FIG. 4, the temperature sensor delivers metal-temperature information to a power regulator which automatically regulates the amount of power from the heating coil power source, such as an MG set or static inverter, to the induction heating coil 18 to maintain such temperature at a selected value.

At intervals which coincide with the periodic instantaneous demands of the molten-metal-using machine or apparatus 5, the inlet stopper valve 27 momentarily will be opened by operation of pneumatic cylinder 48, FIG. 1, to unseat from the upper end of the measuring chamber member 23, FIG. 3, to permit molten metal 21 from the outer crucible 7 to flow into and fill the measuring chamber 24 within such member 23. Following reclosure of the inlet stopper valve 27 by release of cylinder 48 and coincidental with filling times for the moltenmetal-using apparatus 5, the outlet stopper valve 26 will be raised by cylinder 46, FIg. l, to permit the single-shot molten metal volume in the measuring chamber 24 to empty by way of the delivery nozzle 30 into such apparatus 5. A small annular clearanceway 70 between the two stopper valve stems 42 and 44 enable such emptying and filling of the measuring chamber 24.

From the foregoing, it will be appreciated that the semicontinuous molten metal supplying apparatus of the present invention provides a highly compact arrangement for supplying molten metal to a machine or device utilizing such metal, and that by virtue of its employment of an induction heated crucible under automatic power regulation, together with the induction stirring effect of such coil, a relatively precise temperature demand condition for such metal can be provided with relative ease to assure successful performance of such metal'utilizing devices. At the same time, by virtue of providing a precise measured volume for supply to such metal-using device prior art problems arising from over and under supply of metal thereto are overcome. Still further, by virtue of encircling the measuring member 23 with the temperature-stabilized molten metal 21 of the outer crucible 7, stabilization of the temperature of the measured volume filling chamber 24 is thereby also assured. Yet still further, by virtue of such encir clement of the valve seat areas 34 and 40 for the stopper valves 26 and 27 also with the molten metal 21 in the outer crucible 7, such seat areas tend to remain free of solid metal deposit to enjoy prolonged stickfree operation of such valves.

It is also of significance that the exemplified induction crucible 7 of FIG. 3 is particularly suited for rapid and uniform distribution of heat within the molten metal volume 21, by virtue of extension of the helical induction coil 18 the full height of such volume, which enhances uniform induction heating and stirring of such metal, and by virtue of the hollow cylindrical shape of such volume 21, it tends to be closely coupled to the coil 18 throughout its radial depth.

I claim as my invention:

1. Apparatus for supplying molten metal to molten-metalusing means which requires supply of a particular amount of molten metal periodically during its operation,

said apparatus comprising,

said measuring volume means is in the form of a hollow member having inlet and outlet openings at its top and bottom, respectively, both so located vertically as to lie within the level of molten metal in said crucible and said valve means is in the form of a pair of axially movable coaxially arranged normally closed independently openable stopper valves, having a venting passage clearanceway therebetween, which cooperate with the top and bottom of said hollow member, respectively, for selective control of the inlet and outlet openings therein. 

1. Apparatus for supplying molten metal to molten-metal-using means which requires supply of a particular amount of molten metal periodically during its operation, said apparatus comprising, a molten-metal-holding heating crucible having a surrounding induction coil for electromagnetic coupling with such metal to effect induction heating and stirring thereof, feed means for introducing input metal to said crucible, energization means for said induction coil, and molten metal delivery means including a measuring volume means capable of holding substantially only the aforesaid particular amount of molten metal, and valve means for effecting periodic transfer of molten metal consecutively from said crucible to said measuring volume means and from said measuring volume means to the aforesaid molten-metal-using means, said measuring volume means is in the form of a hollow member having inlet and outlet openings at its top and bottom, respectively, both so located vertically as to lie within the level of molten metal in said crucible, and said valve means is in the form of a pair of axially movable coaxially arranged normally closed independently openable stopper valves, having a venting passage clearanceway therebetween, which cooperate with the top and bottom of said hollow member, respectively, for selective control of the inlet and outlet openings therein. 